1. Field of the Invention
This invention relates to photographic elements and more particularly to photographic elements having a light-sensitive silver halide layer and a transparent magnetic recording layer.
2. Description of Related Art
It is known from various U.S. patents, including: U.S. Pat. Nos. 3,782,947; 4,279,945; 4,990,276; 5,217,804; 5,147,768; 5,229,259, and others; to include in a light-sensitive silver halide photographic element a transparent magnetic recording layer. Such elements are advantageous because they can be employed to record images by the customary photographic process while at the same time information can be recorded into and read from the magnetic recording layer by the techniques similar to that employed in the magnetic recording art.
A difficulty, however, arises in that magnetic recording layers generally employed in the magnetic recording industry are opaque, not only because of the nature of the magnetic particles, but also because of the requirements that the recording layer contains other additives which further create problems with regard to the optical characteristics of the layer. Thus, the nature and quantity of any materials added to the magnetic recording layer must not interfere with the optical characteristics of the layer. Also, the requirements of recording and reading of the magnetic signal from a transparent magnetic layer present on a photographic element are more stringent than that found in conventional magnetic recording because of the loading of the magnetic particles in the transparent magnetic layer and the nature of the photographic element.
That is, the presence of the magnetic recording layer cannot interfere with the primary function of the photographic element which is to achieve realistic reproductions of the original image. In addition, the magnetic recording layer must be capable of accurately recording the information applied thereto and reading out the information on demand. This is particularly difficult because the loading of the magnetic particles in the transparent layer must be such as to not interfere with the quality of the photographic elements.
Finally, the photographic element and particularly the transparent magnetic recording layer provided thereon must be capable of repeated use in both the recording and reading mode and, therefore, must be durable, abrasion resistant and scratch resistant so as not to adversely affect the quality of the photographic element. For example, during the residence of the film in a camera, entries may be made to the magnetic recording layer for every exposure, and an indeterminate number of read operations are conducted depending on the particular application to which the film is used. This also is true in the processing of the film and in subsequent use of the processed film for additional copies, enlargements and the like.
These requirements are exacerbated by the curl present in photographic elements as a result of the presence of the hydrophilic layers and the core set from being tightly wound on small mandrels. A consequence of the curl is that much higher pressures on the photographic element than employed in coventional magnetic recording and particularly on the magnetic layer must be employed to flatten the magnetic layer and hold it tightly against the magnetic recording and reading heads. This high pressure coupled with the speed at which the element moves past the head causes unusually high stress in the magnetic recording layer rendering it susceptible to failure.
It can, therefore, be readily seen that it is highly desirable to provide photographic elements having a transparent magnetic recording layer exhibiting improved magnetic and photographic performance as well as improved running durability, abrasion resistance and scratch resistance. This goal is extremely difficult to achieve because of the nature and concentration of the magnetic particles required to provide sufficient signal to write and read magnetically stored data, the effect of any noticeable color, haze, or grain associated with the magnetic layer on the photographic layers and the effect of the magnetic layer on the optical density and granularity of the photographic layers. Thus, all of these various characteristics must be considered both independently and cumulatively in order to arrive at a commercially viable photographic element containing a transparent magnetic recording layer that will withstand repeated and numerous passages through the recording and reading zones of a suitable apparatus.